1. Field of Invention
The present invention relates generally to a document scheduling scheme for improving the productivity of a networked printer.
2. Description of Related Art
Traditionally, a printer prints a job as the job arrives to the printer. In a networked printer environment, a network server presents the jobs queued at the network to the printer for printing sequentially. The printer is traditionally a two-phase work center. In the first phase of the printing function, the printer processes in the job for rasterization. The process is known as raster image processing (RIP). In the second phase of the printing function, the printer prints the job. If there are some jobs that have complex color graphics, the electronic subsystem (ESS) in the printer takes a long time to rasterize the image. In this situation, the first phase printer RIP function for a complex job results in an image output terminal (IOT) in the printer staying idle. Thus, for example, a simple black and white printing job may have to wait a long period while the complex job is ripped and eventually printed. Therefore, the printers productivity is not fully utilized.
This invention provides a scheduling scheme that uses an estimated rasterization execution time (RET) to improve the productivity of printers, and particularly color printers. A networked color printer gets a variety of jobs, which simplistically can be classified into two categories, e.g., simple and complex. Because print jobs have different levels of complexities, a longer RET may be required for some jobs, e.g., complex jobs, than for others, e.g., simple jobs. For example, a complex print job which includes color graphics, color print, different font changes or a variety of style formats such as, italic, bold and other styles, will have a longer RET than a simple black and white print job. If a print job is pre-scanned to estimate the RET before the print job arrives at the printer, it is possible to schedule those print jobs with a shorter RET ahead of those print jobs with a longer RET, thus improving productivity of the printer. This allows the use of one set of color printers capable of efficiently doing both color and black and white jobs, instead of using separate color and black and white printers.
A printer can be viewed as two work centers in series, an ESS work center and an IOT work center. The ESS work center of a printer takes a file and RIPs it. When a file is ripped, all of the information in the document file is converted into a bitmap. Then, the ESS work center of the printer sends the document file to the printer""s second work center, the IOT. The IOT prints the file. However, the IOT cannot print the file until after the RIP function has been performed. To get the highest efficiency from the series combination of the ESS and the IOT, the functions of both the ESS and the IOT must be balanced.
Since the majority of print jobs fall into the simple category, users are frustrated with waiting for complex jobs to finish which were submitted ahead of their jobs. Therefore, to balance the functions between the ESS and the IOT, the present invention uses a two queue approach. For example, the print jobs which require a minimum amount of time for the ESS to process, i.e., the simple jobs, are placed in one queue, e.g., a simple queue, and the print jobs which are more complex and time consuming for the ESS are placed in a second queue, e.g., a complex queue. The print jobs which are in the simple queue are ripped and printed first, even if these print jobs arrive after the complex jobs, and then the print jobs in the complex queue are processed. This reduces the IOT idle time which significantly improves the wait time for simple print jobs.
A print driver, preferably located in the workstation, pre-scans a document and takes the document file and converts it into a postscript (page description language, PDL) print ready file. Additionally, the print driver attaches a header to the file. The header will identify the complexity level of the document file, including whether the file is color or black and white, e.g., simple or complex. The printer, or print server, will read the header information and, based on the header information, schedules the print jobs by placing the document file into an appropriate queue, e.g., a simple queue or a complex queue. Print jobs in the simple queue will have a higher priority than print jobs in the complex queue.
The two queue approach is for simplicity purposes. Alternatively, a single queue can be used in which the jobs are arranged in ascending order of their RET estimates. The jobs with the smallest RET estimates will be ripped and printed first.
A priority override structure may also be included in this invention. For example, a customer will be allowed to assign a priority level to a specific print job regardless of whether the job is allocated to the simple queue or the complex queue. Authorized customers with access authorization will be able to advance the priority of specific print jobs. Thus, the printer will take this priority override information and process it accordingly. Therefore, jobs with the highest priority will print first, regardless of the complexity level. However, priority override capabilities should be limited to a few individuals to maintain the overall efficiency of the system.
This invention provides systems and methods for reducing wait time for simple print jobs by scheduling a document based on rasterization execution time estimate.
This invention separately provides systems and methods for assigning a complexity rating to print jobs.
This invention separately provides systems and methods for pre-scanning document files via a workstation print driver.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of this invention.